1. Field of the Invention
The present invention relates to formed fuels, processes for forming the same and processes for utilizing the same in steel making.
2. Description of the Prior Art
Perhaps the most commonly used method of melting iron is through the use of a cupola wherein coke, a fluxing material such as limestone, and a metallic material are charged. The coke is ignited and air is blasted into the bottom of the cupola to generate intense heat, melting the iron which then trickles down through the fluxing material and the coke to the bottom of the cupola. A molten slag is formed on the top of the charge and typically comprises coke ash and similar materials.
The coke used in the charge in most steel-making processes today is high-quality metallurgical grade coke which is produced by the distillation (in the absence of oxygen) of coal.
After the distillation to form high-grade metallurgical coke, handling methods in common use are such that the relatively brittle chunks of coke break up and form a very fine particulate form of coke called "coke breeze." In general, all coke particles that pass through a one-inch mesh size are too fine for use in a cupola melting process, and are typically discarded by the steel-making industry.
The reason that coke breeze cannot be used in the steel making industry is that the air blast and intense heat either immediately consume the coke breeze or blow it out of cupola, with the coke breeze contributing little or nothing to yield heat and potentially creating the danger of explosion. Coke breeze also tends to reduce the necessary freedom of air flow through the melt.
Typically, coke breeze will represent about 10% of the total amount of coke fed to a cupola.
Attempts have been made in the prior art to form coke breeze into briquettes. However, prior art briquettes have been subject to a number of problems, viz.
The most common problem of prior art coke briquettes is that the briquettes have been too brittle to withstand bulk handling and crumble or break into coke breeze.
Attempts have been made to use high proportions of binder to overcome this problem, but when the amount of binder has been increased to an extent that the briquettes are no longer brittle, the amount of binder is so high that it leads to an undesirable amount of slag in the steel-making process and actually can introduce undesirable impurities into the steel, reducing product value.
A further problem of many prior art processes is that high heating conditions are required to form the charge to be briquetted, very high pressures are necessary to form the briquette, or high temperature or extended curing times are necessary to form the briquette.
The present invention permits all of the above disadvantages of the prior art to be overcome, and provides a product completely compatible with the charge to a steel-making process which is substantially identical in product characteristics to high-grade metallurgical coke.
In addition, the product of the present invention is formed by a simple process at ambient conditions and requires no complicated processing equipment.
Finally, in the product of the present invention, very low amounts of binder are used, whereby the carbon content of the product of the present invention is suitable for steel making in a manner similar to high-grade metallurgical coke.
U.S. Pat. Nos. 2,665,977, Engelhart, 4,063,944, Behring, 4,078,902, Olson, and 3,762,886, Triska, disclose fuel briquettes using cement as a binder, certain of these patents disclosing coke breeze being bound by the cement.
Fuel briquettes formed in accordance with this type of prior art is subject to the fault that they exhibit a high ash content and cement is alien to steel-making processes.
U.S. Pat. Nos. 2,508,878, Yates et al., and 2,979,388, Brown et al., disclose the use of organic materials such as asphalt, pitches, thermal tars, and the like, as a binder for a carbonaceous material. Coke breeze is not disclosed, and the products of these two patents differ substantially from those of the present invention. The Yates et al. patent does disclose the combination of magnesium oxide, carbon, and pitch as a binder, but the processing sequence described is a high-temperature sequence and the briquettes are heated in the absence of air to carbonize the pitch.
These two patents are subject to the fault that binder materials as are utilized are essentially viscous materials, and they break down during the steel-making process at too early a stage to effectively function in a manner similar to coke.
U.S. Pat. No. 3,676,162, Mehler et al., discloses a basic refractory material for lining steel converters which comprises sintered magnesia bonded with sodium polyphosphate or magnesium sulphate and impregnated with liquid tar. Such a product has a utility exactly opposed to that of the product of the present invention.
U.S. Pat. Nos. 3,879,209 and 4,059,455, both to Limes et al., and 3,960,580, Stierli et al., disclose fast-setting concrete compositions which include magnesia and ammonium polyphosphate. There is no suggestion in any of these patents that the binder systems disclosed would be useful for binding a fine material such as coke breeze, nor, of course, that the binder systems described could be utilized to form a fuel briquette with the unique characteristics of the present invention.
The following patents generally deal with briquetting finely divided materials: U.S. Pat. Nos. 1,507,674, Nagel, 1,661,636, Simpson, 2,029,309, Curtis et al., 2,711,951, West et al., 3,617,254, Emperato, Jr., 3,674,449, Schmalfeld et al., 3,730,692, Halowaty et al., 3,838,988, Sanada et al., 3,841,849, Beckmann, and 4,015,977, Crawford.
In all of these patents, there is no disclosure of the unique fuel briquette of the present invention nor the properties thereof.
U.S. Pat. Nos. 3,285,758, Limes et al., and 3,413,385, Komac et al., deal with basic refractory compositions and processes for repairing refractory walls, respectively, wherein a magnesia/ammonium phosphate binder is used.
U.S. Pat. No. 3,708,317, Owen, discloses a metallurgical furnace lining and U.S. Pat. No. 3,826,662, Paolini, discloses a trowlable patching mix for refractory linings containing coke breeze, fire clay and pitch.